TORONTO - A new study says that women who have donated a kidney are at higher risk of developing gestational hypertension or a potentially dangerous condition called pre-eclampsia during pregnancies that follow the donation.

The study suggests the increase in risk is not enormous, and in fact most women who have donated a kidney can safely carry a pregnancy to term.

But the authors say women of child-bearing age considering donating a kidney should be informed.

Women who have donated a kidney face an 11 per cent risk of developing one of these conditions; for women who have both kidneys, it's a five per cent chance.

The study was presented Friday at a meeting of the American Society of Nephrology and is being published in the New England Journal of Medicine.

The lead author says the Number 1 question women who are thinking about donating a kidney ask is if giving up a kidney will affect their ability to have healthy pregnancies later.

Dr. Amit Garg is a scientist at Ontario's Institute for Clinical Evaluative Sciences and director of the living donor program at Lawson Health Research Institute at the London Health Sciences Centre.

Garg says previous studies have shown conflicting results on this question, so he and his co-authors set out to see if they could find a clearer answer.

He says he's talked with some women who have donated kidneys through his program, to get their take on the findings.

"Many women who we've talked to when they hear about these results still feel comfortable in their donation decision. And we fully expect many women who come forward to donate kidneys when hearing this information will still wish to proceed with donation," says Garg, a nephrologist or kidney specialist.

He notes most living donors are giving up an organ out of love. While some people donate organs to strangers in need, the majority of donations are among family members.

The study looked at medical records of all women in Ontario who donated a kidney between July 1, 1992 and April 20, 2010 who went on to have at least one pregnancy after the donation, and compared their experiences to similar women who had not donated a kidney.

Fans of the TV show "Downton Abbey" will remember pre-eclampsia as the condition that killed Lady Sibyl during childbirth. It is the leading cause of maternal mortality.

Pre-eclampsia (the precursor to full-blown eclampsia) is a marked by a trio of classic symptoms — fluid retention, headaches and high blood pressure. While it can be fatal if untreated, ending the pregnancy by inducing delivery or performing a caesarean section will cure the condition.